1. Field of the Invention
The present invention generally relates to finishing printed sheets of paper and, more particularly, to stapling and collecting printed sheets of paper.
2. Background Information
A system for finishing printed sheets into booklets is described in U.S. Pat. No. 6,099,225 (Allen et al., hereafter referred to as xe2x80x9cthe Allen patentxe2x80x9d), hereby incorporated by reference in its entirety, where most finishing operations are performed on a sheet-by-sheet basis using precise paper positioning. The system also uses a transverse tool carrier for cutting, scoring, folding, punching, and stapling booklet sheets. Also described in the Allen patent is an inverted V-shaped workpiece for collecting folded booklet sheets. However, no specific method for aligning a stapler to the V-shaped workpiece is disclosed in the Allen patent.
Another system for making saddle-stitched booklets on a sheet-wise basis is disclosed in PCT No. WO 00/18583 (Trovinger et al., hereafter referred to as xe2x80x9cthe Trovinger PCTxe2x80x9d), hereby incorporated by reference in its entirety. In this system, individual folded booklet sheets are forwarded from a folding device to a reciprocating saddle. This operation begins with the saddle at a first position, where an individual folded sheet is initially advanced (e.g., by rollers) from an upstream, folding device to the saddle, such that the leading side of the sheet is positioned to rest on the front side of the saddle, while the trailing side of the sheet remains supported or under the control of the upstream device.
As the leading side is advanced to the point where the fold of the folded sheet rests on the top edge of the saddle, the saddle is moved along rails towards a second position. Due to the movement of the saddle, the trailing side of the sheet is naturally released or cleared from the upstream device and falls toward the back side of the saddle. When the saddle reaches the second position, the transfer of the folded sheet from the upstream device to the saddle is complete, with the fold and the trailing side resting on the top edge and the back side of the saddle, respectively.
The above steps are repeated until a required number of booklet sheets have been collected on the saddle. The sheets are then stapled together on the saddle, where a stapler carriage is moved and operated as a unit separate from the saddle. In other words, the stapler carriage and its attached stapler head unit travel along stapler guide rails lying on one axis, while the saddle and its attached clinch portions moves along saddle guide rails lying in another axis. The saddle moves independently of the stapler guide rails, thereby allowing the distance between the saddle and the stapler carriage to change in the two axes while the saddle travels between the first and second positions.
Due to the independent movement of the stapler head unit and the saddle in the Trovinger PCT, accurate alignment between the two is difficult. Alignment of these device is important to insure properly formed staples, and such alignment may need to be within xc2x10.1 mm, depending on, for example, the stapler design and manufacture. Errors relating to alignment can be due to tolerance stack-up errors, normal mechanical clearances, excessive deflection, as well as servo or motion errors.
Some commercial booklet making devices attempt to address stapler alignment with the use of two fixed-position, pass-through staple units, where no relative movement occurs between a sheet collecting device and the staple units. The method of using fixed-position staple units can not, however, be easily used for sheet-wise operations. Multiple fixed-position staple units also increase a cost of a booklet making device.
Accordingly, it would be desirable to provide a sheet collecting system for sheet-wise operations for providing proper alignment between stapling and collecting portions.
The present invention is directed to a sheet collecting apparatus where a sheet collecting device and a stapler are combined into one unit, thereby eliminating misalignment between the two devices.
According to an exemplary embodiment of the present invention, a sheet collecting apparatus in a sheet-wise booklet making system is provided, comprising a collecting device for supporting folded sheets of material in a stack arranged for stapling, and a stapling device for stapling the folded sheets of material supported by the collecting device. The collecting device and the stapling device are attached to a movable frame such that the stapling device remains aligned with the collecting device during movement of the movable frame.
According to another embodiment of the present invention, a method for stapling a booklet comprises the steps of providing a collecting device and a stapling device both mounted on a movable frame, delivering a booklet sheet, and stapling a folded edge of the booklet sheet with the stapling device when the movable frame is at a second position, wherein the stapling device and the collecting device remain aligned while the movable frame is moved between a first position and the second position.